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Peripheral Circulation and Regulation

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Transport blood through most all body parts from left ventricle ... Tunica intima. Endothelium. Tunica media. Vasoconstriction. Vasodilation. Tunica adventitia ... – PowerPoint PPT presentation

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Title: Peripheral Circulation and Regulation


1
Chapter 21
  • Peripheral Circulation and Regulation

2
Peripheral Circulatory System
  • Systemic vessels
  • Transport blood through most all body parts from
    left ventricle and back to right atrium
  • Pulmonary vessels
  • Transport blood from right ventricle through
    lungs and back to left atrium
  • Blood vessels and heart regulated to ensure blood
    pressure is high enough for blood flow to meet
    metabolic needs of tissues

3
Blood Vessel Structure
  • Arteries
  • Elastic, muscular, arterioles
  • Capillaries
  • Blood flows from arterioles to capillaries
  • Most of exchange between blood and interstitial
    spaces occurs across the walls
  • Blood flows from capillaries to venous system
  • Veins
  • Venules, small veins, medium or large veins

4
Capillaries
  • Capillary wall consists mostly of endothelial
    cells
  • Types classified by diameter/permeability
  • Continuous
  • Do not have fenestrae
  • Fenestrated
  • Have pores
  • Sinusoidal
  • Large diameter with large fenestrae

5
Capillary Network
  • Blood flows from arterioles through
    metarterioles, then through capillary network
  • Venules drain network
  • Smooth muscle in arterioles, metarterioles,
    precapillary sphincters regulates blood flow

6
Structure of Arteries and Veins
  • Three layers except for capillaries and venules
  • Tunica intima
  • Endothelium
  • Tunica media
  • Vasoconstriction
  • Vasodilation
  • Tunica adventitia
  • Merges with connective tissue surrounding blood
    vessels

7
Structure of Arteries
  • Elastic or conducting arteries
  • Largest diameters, pressure high and fluctuates
  • Muscular or medium arteries
  • Smooth muscle allows vessels to regulate blood
    supply by constricting or dilating
  • Arterioles
  • Transport blood from small arteries to capillaries

8
Structure of Veins
  • Venules and small veins
  • Tubes of endothelium on delicate basement
    membrane
  • Medium and large veins
  • Valves
  • Allow blood to flow toward heart but not in
    opposite direction
  • Atriovenous anastomoses
  • Allow blood to flow from arterioles to small
    veins without passing through capillaries

9
Blood Vessel Comparison
10
Aging of the Arteries
  • Arteriosclerosis
  • General term for degeneration changes in arteries
    making them less elastic
  • Atherosclerosis
  • Deposition of plaque on walls

11
Pulmonary Circulation
  • Moves blood to and from the lungs
  • Pulmonary trunk
  • Arises from right ventricle
  • Pulmonary arteries
  • Branches of pulmonary trunk which project to
    lungs
  • Pulmonary veins
  • Exit each lung and enter left atrium

12
Systemic Circulation Arteries
  • Aorta
  • From which all arteries are derived either
    directly or indirectly
  • Parts
  • Ascending, descending, thoracic, abdominal
  • Coronary arteries
  • Supply the heart

13
Branches of the Aorta
14
Major Arteries
15
Head and Neck Arteries
16
Arteries of the Brain
17
Head and Thorax Major Arteries
18
Arteries of Upper Limb and Shoulder
19
Arteries of Abdomen and Pelvis
20
Arteries of Pelvis and Lower Limb
21
Arteries of Lower Limb
22
Systemic Circulation Veins
  • Return blood from body to right atrium
  • Major veins
  • Coronary sinus (heart)
  • Superior vena cava (head, neck, thorax, upper
    limbs)
  • Inferior vena cava (abdomen, pelvis, lower limbs)
  • Types of veins
  • Superficial, deep, sinuses

23
Major Veins
24
Veins of Head and Neck
25
Head and Thorax Veins
26
Veins of Shoulder and Upper Limb
27
Veins of Thorax
28
Hepatic Portal System
29
Veins of Abdomen and Pelvis
30
Veins of Pelvis and Lower Limb
31
Veins of Lower Limb
32
Dynamics of Blood Circulation
  • Interrelationships between
  • Pressure
  • Flow
  • Resistance
  • Control mechanisms that regulate blood pressure
  • Blood flow through vessels

33
Laminar and Turbulent Flow
  • Laminar flow
  • Streamlined
  • Outermost layer moving slowest and center moving
    fastest
  • Turbulent flow
  • Interrupted
  • Rate of flow exceeds critical velocity
  • Fluid passes a constriction, sharp turn, rough
    surface

34
Blood Pressure
  • Measure of force exerted by blood against the
    wall
  • Blood moves through vessels because of blood
    pressure
  • Measured by listening for Korotkoff sounds
    produced by turbulent flow in arteries as
    pressure released from blood pressure cuff

35
Blood Pressure Measurement
36
Blood Flow, Poiseuilles Lawand Viscosity
  • Poiseuilles Law
  • Flow decreases when resistance increases
  • Flow resistance decreases when vessel diameter
    increases
  • Viscosity
  • Measure of resistance of liquid to flow
  • As viscosity increases, pressure required to flow
    increases
  • Blood flow
  • Amount of blood moving through a vessel in a
    given time period
  • Directly proportional to pressure differences,
    inversely proportional to resistance

37
Critical Closing Pressure, Laplaces Law and
Compliance
  • Vascular compliance
  • Tendency for blood vessel volume to increase as
    blood pressure increases
  • More easily the vessel wall stretches, the
    greater its compliance
  • Venous system has a large compliance and acts as
    a blood reservoir
  • Critical closing pressure
  • Pressure at which a blood vessel collapses and
    blood flow stops
  • Laplaces Law
  • Force acting on blood vessel wall is proportional
    to diameter of the vessel times blood pressure

38
Physiology of Systemic Circulation
  • Determined by
  • Anatomy of circulatory system
  • Dynamics of blood flow
  • Regulatory mechanisms that control heart and
    blood vessels
  • Blood volume
  • Most in the veins
  • Smaller volumes in arteries and capillaries

39
Cross-Sectional Area
  • As diameter of vessels decreases, the total
    cross-sectional area increases and velocity of
    blood flow decreases
  • Much like a stream that flows rapidly through a
    narrow gorge but flows slowly through a broad
    plane

40
Pressure and Resistance
  • Blood pressure averages 100 mm Hg in aorta and
    drops to 0 mm Hg in the right atrium
  • Greatest drop in pressure occurs in arterioles
    which regulate blood flow through tissues
  • No large fluctuations in capillaries and veins

41
Pulse Pressure
  • Difference between systolic and diastolic
    pressures
  • Increases when stroke volume increases or
    vascular compliance decreases
  • Pulse pressure can be used to take a pulse to
    determine heart rate and rhythmicity

42
Capillary Exchange andInterstitial Fluid Volume
Regulation
  • Blood pressure, capillary permeability, and
    osmosis affect movement of fluid from capillaries
  • A net movement of fluid occurs from blood into
    tissues. Fluid gained by tissues is removed by
    lymphatic system.

43
Fluid Exchange Across Capillary Walls
44
Vein Characteristics andEffect of Gravity on
Blood Pressure
  • Vein Characteristics
  • Venous return to heart increases due to increase
    in blood volume, venous tone, and arteriole
    dilation
  • Effect of Gravity
  • In a standing position, hydrostatic pressure
    caused by gravity increases blood pressure below
    the heart and decreases pressure above the heart

45
Control of Blood Flow by Tissues
  • Local control
  • In most tissues, blood flow is proportional to
    metabolic needs of tissues
  • Nervous System
  • Responsible for routing blood flow and
    maintaining blood pressure
  • Hormonal Control
  • Sympathetic action potentials stimulate
    epinephrine and norepinephrine

46
Local Control of Blood Flow by Tissues
  • Blood flow can increase 7-8 times as a result of
    vasodilation of metarterioles and precapillary
    sphincters in response to increased rate of
    metabolism
  • Vasodilator substances produced as metabolism
    increases
  • Vasomotion is periodic contraction and relaxation
    of precapillary sphincters

47
Nervous Regulation of Blood Vessels
48
Short-Term Regulation ofBlood Pressure
  • Baroreceptor reflexes
  • Change peripheral resistance, heart rate, and
    stroke volume in response to changes in blood
    pressure
  • Chemoreceptor reflexes
  • Sensory receptors sensitive to oxygen, carbon
    dioxide, and pH levels of blood
  • Central nervous system ischemic response
  • Results from high carbon dioxide or low pH levels
    in medulla and increases peripheral resistance

49
Baroreceptor Reflex Control
50
Baroreceptor Effects
51
Chemoreceptor Reflex Control
52
Effects of pH and Gases
53
Long-Term Regulation of Blood Pressure
  • Renin-angiotensin-aldosterone mechanism
  • Vasopressin (ADH) mechanism
  • Atrial natriuretic mechanism
  • Fluid shift mechanism
  • Stress-relaxation response

54
Renin-Angiotensin-AldosteroneMechanism
55
Vasopressin (ADH) Mechanism
56
Long Term Mechanisms
  • Fluid shift
  • Movement of fluid from interstitial spaces into
    capillaries in response to decrease in blood
    pressure to maintain blood volume
  • Stress-relaxation
  • Adjustment of blood vessel smooth muscle to
    respond to change in blood volume
  • Atrial natriuretic
  • Hormone released from cardiac muscle cells when
    atrial blood pressure increases, simulating an
    increase in urinary production, causing a
    decrease in blood volume and blood pressure

57
Shock
  • Inadequate blood flow throughout body
  • Three stages
  • Compensated Blood pressure decreases only a
    moderate amount and mechanisms able to
    reestablish normal blood pressure and flow
  • Progressive Compensatory mechanisms inadequate
    and positive feedback cycle develops cycle
    proceeds to next stage or medical treatment
    reestablishes adequate blood flow to tissues
  • Irreversible Leads to death, regardless of
    medical treatment
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